Adhesive compositions are widely used to bond elastomeric materials, including vulcanizable elastomeric materials, to a variety of substrates. Generally, adhesives known to be effective as rubber-to-metal bonding agents can be limited with regard to the type of elastomer to be bonded. In addition, adhesive compositions that effectively bond sulfur-cured elastomeric materials, such as natural rubber compositions, do not necessarily exhibit the same level of performance when used to bond specialty elastomers, such as silicone rubbers.
Silane adhesive compositions have been developed to bond elastomeric materials, particularly silicon elastomer-based materials, to various substrates. Many silane adhesive compositions rely on organofunctional silanes as the active bonding agent. Due to the moisture sensitive nature of the organofunctional silane compounds, traditional silane adhesive compositions have relied on organic solvents to form a stable and workable solution. See for example, U.S. Pat. Nos. 4,308,071 and 4,031,120 to Gervase; U.S. Pat. No. 4,618,389 to Agodoa; U.S. Pat. No. 3,678,003 to Kaiser; U.S. Pat. No. 3,022,196 to Jenkins et al.; and U.S. Pat. No. 4,690,966 to Rende, Jr. However, there are increasing environmental concerns associated with the use of solvent-based systems.
Attempts have been made to provide aqueous silane adhesive systems. See for example, U.S. Pat. No. 2,979,420 to Harper; U.S. Pat. Nos. 5,532,314 and 5,178,675 to Sexsmith; and U.S. Pat. No. 4,921,987 to Hitze et al. However, many aqueous systems can suffer from low bond strength, short shelf life, and other characteristics which are disadvantageous in the production of vulcanizable elastomer/substrate articles and other products.